Composition of matter for the production of graphite powder

ABSTRACT

The present invention relates to a composition for the production of a graphite powder, suitable for making high performance lithium-ion battery anodes and other applications. The composition of matter comprises a biochar, a metal and graphite. The biochar is typically derived from the pyrolysis of woody biomass. The metal is typically a transition metal derived from the decomposition and reduction of an organic or inorganic metallic compound. The graphite is highly crystalline and has a wide range of morphologies or structures.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.17/659,985, filed on Apr. 20, 2022, which is a continuation ofInternational Application Serial No. PCT/NZ2021/050146, filed on Aug.25, 2021, which claims the benefit of U.S. Provisional ApplicationSerial No. 63/177,705, filed on Apr. 21, 2021, the entire disclosures ofwhich are incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates to a composition of matter suitable forthe production of a graphite powder, suitable for making highperformance lithium-ion battery anodes and other applications. Thecomposition of matter comprises a biochar, a metal and graphite.

BACKGROUND OF THE INVENTION

Lithium-ion batteries have become ubiquitous in society, being used inanything from portable electronic equipment to power tools to electricalvehicles. The rise in utilisation of lithium-ion batteries has driventhe development to explore new and improved materials of construction toincrease performance In addition, certain lithium-ion battery componentsare limited in supply and will only increase in scarcity as demand growswith the global transition to an electrical infrastructure rather than afossil fuel based one. For this reason, there is a concerted effort tofind alternative raw material sources, most suitably from renewableresources to ensure sustainability. One of the components in thelithium-ion battery that is in short supply is graphite.

Graphite is either synthesised from petroleum-based precursors orobtained from natural deposits. Some carbon materials, such as coke andmesophase pitch can be transformed to graphite simply by heating andsuch materials are termed graphitizable. Other carbon materials, forexample char and some carbonised polymers, require the addition of othercomponents in order to facilitate the transformation into graphite[1,2]. However, for application in lithium-ion batteries very specificrequirements must be met. Only graphite materials with a very narrowrange of properties are capable of delivering the performance essentialfor modern applications. Innumerable possibilities exist for arriving ata mixture of graphite, catalyst and residual char. However, only a smallsubset of such mixtures result in a composition of matter suitable forfurther processing into graphite and eventual use in lithium-ionbatteries.

The present invention specifically discloses a composition of matterappropriate for producing a graphite powder suitable for use incommercial, high performance lithium-ion batteries. The disclosure laysdown the ranges required, not only of the elemental composition but alsothe relative amounts of the distinguishable carbon allotropes.Furthermore, the properties associated with the structure andcrystalline state of each of the components are definable.

SUMMARY OF THE INVENTION

The present disclosure provides a composition of matter comprising amixture of biochar, a metal and graphite. This mixture has a set ofunique properties which allows it to be processed into a highperformance lithium-ion battery anode powder. The mixture may also beprocessed into graphite powders for use in other applications. Methodsfor producing this composition of matter are also disclosed.

In one aspect there is provided a composition of matter comprising amixture of biochar, a metal and graphite. In one embodiment the mixturehas (a) a graphite content of between about 25 to 65 percent by weight,(b) a metal content of between about 15 to 75 percent by weight and (c)a biochar content of between 1 and 35 percent by weight.

In one embodiment the graphite has a d-spacing of between about 0.3354and about 0.3401 nm.

In one embodiment the electrochemical capacity of the graphite is atleast 200 mAh/g, more preferably the electrochemical capacity of thegraphite is greater than 300 mAh/g.

In one embodiment the specific surface area of the graphite is betweenabout 0.2 to about 50 m²/g. More preferably the specific surface area ofthe graphite is less than about 20 m²/g.

In one embodiment the graphite exhibits a “Coulombic” or first cycleefficiency of greater than 60%, more preferably greater than 80%.

In one embodiment the graphite content in the mixture is in particulateform.

In one embodiment the metal content in the mixture is in particulateform.

In one embodiment the biochar content in the mixture is in particulateform.

In one embodiment the graphite, metal and biochar content are all inparticulate form.

In one embodiment the mixture is a binary mixture having an elementalcomposition of between about 25 to 75 percent carbon, made up of biocharand graphite and between about 75 to 25 percent of a selected metal.

In one embodiment the biochar content is derived from woody biomassheated to temperatures of between about 200 and 1000 degrees Celsius.

In one embodiment the metal is a transition metal. In one embodiment thetransition metal is selected from chromium, zirconium, molybdenum,ruthenium, rhodium, palladium, silver, cadmium, zinc, copper, nickel,cobalt, iron, manganese, chromium, vanadium or any combination thereof.

In one embodiment the particulate sizes of the biochar component areless than about 1 millimetre.

In one embodiment the particulate sizes of the metal component are lessthan about 1 millimetre.

In one embodiment the particulate sizes of the graphite component areless than about 1 millimetre.

In one embodiment the particulate sizes of all the components are lessthan 1 millimetre.

In one embodiment the total graphitic carbon content in the mixture isgreater than about 55%wt.

In one aspect there is a method of producing a mixture as defined above;the method including the steps of:

-   -   i) thermally treating biomass in particulate form at a        temperature of between 200 and 1000 degrees Celsius to form a        particulate biochar;    -   ii) combining the resulting biochar with a particulate metal        compound in a wet or a dry form to create a precursor mixture;    -   iii) heating the precursor mixture to between about 400 to about        3000 degrees Celsius under inert conditions to form a graphite        containing mixture;    -   iv) sieving the final mixture to below about 1 mm particulate        size to produce a mixture having (a) a graphite content of        between about 25 to 65 percent by weight, (b) a metal content of        between about 15 to 75 percent by weight and (c) a biochar        content of between 1 and 35 percent by weight.

In one embodiment the biomass is thermally treated in water in ahydrothermal step.

In one embodiment the biomass is thermally treated under inertconditions in a dry pyrolysis step.

In one embodiment the biomass is forestry residue.

In one embodiment the forestry residue is sawdust.

In one embodiment the biomass is woodchip or any other wood-basedmaterial.

In one embodiment the biomass particles are less than about 10 mm In oneembodiment the biomass particles are less than about 1 mm

In one embodiment the particulate sizes of the graphite, metal andbiochar are all less than about 1 millimetre after sieving.

In one embodiment the method includes the further steps such as but notlimited to purification by acid leaching the mixture (or other means),washing and filtering the resulting graphite sample to high puritygraphite. Additional steps may include densification or spheroidizationand carbon coating to further enhance performance

The foregoing and other aspects or advantages of the present inventionwill be apparent to those skilled in the art, using the detaileddescription, images, analytical results and performance test outcomesprovided in this specification.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an image of the microwave applicator used to generate thegraphite samples described in this specification.

FIG. 2A shows an image of the sample crucible placement in the microwaveapplicator. FIG. 2 b shows an image of the sample crucible at hightemperature.

FIG. 3 shows a scanning electron image of the graphite sample generatedduring Example 1.

FIG. 4 shows an XRD diffractogram of the graphite sample generatedduring Example 1.

FIG. 5 shows an image of the large graphite “spheres” generated duringExample 1, which were removed by sieving.

FIG. 6 shows a scanning electron image of the graphite sample generatedduring Example 2.

FIG. 7 shows an XRD diffractogram of the graphite sample generatedduring Example 2.

FIG. 8 shows a scanning electron image of the graphite sample generatedduring Example 3.

FIG. 9 shows an XRD diffractogram of the graphite sample generatedduring Example 3.

FIG. 10 shows an XRD diffractogram of the graphite sample referred to inExample 4.

FIG. 11 shows a particle size distribution of the graphite samplereferred to in Example 4.

FIG. 12 shows the electrochemical behaviour of the graphite samplereferred to in Example 4.

FIG. 13 shows the XRD diffractograms of the graphite samples generatedduring Example 5 and 6.

FIG. 14 is a process diagram showing the overall conversion of biomassto graphite anode powder for lithium-ion batteries.

DETAILED DESCRIPTION OF THE INVENTION

The following description sets forth numerous exemplary configurations,parameters, and the like. It should be recognised, however, that suchdescription is not intended as a limitation on the scope of the presentinvention but is instead provided as a description of exemplaryembodiments.

All references, including patents and patent applications, cited in thisspecification are hereby incorporated by reference. No admission is madethat any reference constitutes prior art. Nor does discussion of anyreference constitute an admission that such reference forms part of thecommon general knowledge in the art, in New Zealand or in any othercountry.

Definitions

In each instance herein, in descriptions, embodiments, examples, andclaims, the terms “comprising”, “including”, etc., are to be readexpansively, without limitation. Thus, unless the context clearlyrequires otherwise, throughout the description and the claims, the words“comprise”, “comprising”, and the like are to be construed in aninclusive sense as to opposed to an exclusive sense, that is to say inthe sense of “including but not limited to”.

As used herein, the articles “a” and “an” are used to refer to one or tomore than one (i.e., to at least one) of the grammatical object of thearticle. By way of example, “an element” can be taken to mean oneelement or more than one element.

The term “about” or “approximately” is used to indicate a broader rangecentred on the given value, and unless otherwise clear from the contextimplies a broader range around the least significant digit, such as“about 1.1” implies a range from 1.0 to 1.2. If the least significantdigit is unclear, then the term “about” implies a factor of two, e.g.,“about X” implies a value in the range from 0.5x to 2x, for example,about 100 implies a value in a range from 50 to 200. Moreover, allranges disclosed herein are to be understood to encompass any and allsub-ranges subsumed therein. For example, a range of “less than 10” caninclude any and all sub-ranges between (and including) the minimum valueof zero and the maximum value of 10, that is, any and all sub-rangeshaving a minimum value of equal to or greater than zero and a maximumvalue of equal to or less than 10, e.g., 1 to 4.

Unless defined otherwise, the scientific and technological terms andnomenclature used herein have the same meaning as commonly understood bya person of ordinary skill to which this disclosure pertains.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope are approximations, the numerical values set forth inspecific non-limiting examples are reported as precisely as possible.Any numerical value, however, inherently contains certain errorsnecessarily resulting from the standard deviation found in theirrespective testing measurements at the time of this writing.Furthermore, unless otherwise clear from the context, a numerical valuepresented herein has an implied precision given by the first significantdigit. Thus, a value 1.105 implies a value from 1.0 to 1.2, whereas110.5 given by 1.105×10², implies a value from 100 to 120.

As used herein the terms “biochar” or “carbonaceous char” or “char” areused interchangeably to mean a material resulting from the thermaldecomposition of a carbonaceous material in an inert atmosphere.

As used herein the term “amorphous” means a material with no long- orshort-range structural ordering, as opposed to a crystal which has anatomic arrangement in the form of a regular lattice, comprised ofrepetitions of a defined unit cell.

As used herein the term “allotropes” means materials with the sameelemental composition, such as pure carbon for example, but withdifferent forms or atomic configurations, for example diamond versusgraphite or amorphous biochar/char versus graphite.

As used herein the term “thermally treated” means any thermal treatmentprocess that is applied to biomass at a temperature sufficient to createa biochar, including hydrothermal and dry pyrolysis.

As used herein the term “high performance” in relation to lithium-ionbattery anode powder, means a graphite powder with a d-spacing ofbetween 0.3354 and 0.3401 nm which results in an electrochemicalcapacity of at least 200 mAh/g and a specific surface area of betweenabout 0.2 to 50 m²/g which results in a “Coulombic” or first cycleefficiency of greater than 60%.

Composite of Biochar, Metal and Graphite

The novel composition of matter described in this specification iscomprised of biochar, a metal and graphite. The biochar is typicallyderived from the pyrolysis of woody biomass. The metal is typically atransition metal derived from the decomposition and reduction of anorganic or inorganic metallic compound. The graphite is highlycrystalline and has a wide range of morphologies or structures. Toproduce the composite of interest, the required precursors (biochar andmetallic compound) are mixed and subjected to a heat treatment procedureat a temperature of between 400 and 3000 degrees Celsius for soak timeperiods of between 60 seconds and 20 hours.

In general, a biochar is produced by pyrolyzing a biomass startingmaterial, such as wood chips, saw dust, forestry residue or waste, orany plant derived feedstock, under an inert atmosphere, for examplenitrogen, at temperatures of between 200 and 1000 degrees Celsius, fortime periods of between a few seconds (“fast” pyrolysis) up to severalhours. Alternatively, the biomass can be converted into char using ahydrothermal approach. Here the char and water can be placed in anautoclave at around 360 degrees Celsius and a pressure of approximately200 bar for the same time periods as pyrolysis, followed by drying. Inall cases the resulting char is comprised mainly of the element carbon,with a so-called fixed carbon content above at least 40% but moreusually above 60%. The remainder is comprised of a set of heteroatoms,mainly hydrogen, oxygen, nitrogen and sulphur. In addition, the char maycontain volatile matter, defined as hydrocarbons, aliphatic or aromatic,which are of high enough molecular weight to not have been vaporisedduring the heat treatment. The exact composition will depend on thepyrolysis conditions and the selected biomass starting material. Thismaterial is conventionally referred to as a “green” char.

Any of the described biochar materials could be selected for thecreation of the aforementioned precursor mixture. It is even possible touse raw biomass directly, which is then transformed into char during theheat treatment procedure. Following subjection of the precursor mixture(biochar and metallic compound) to the stated heat treatment procedure,the char is altered in two ways. Firstly, practically all of theresidual heteroatoms and volatile matter have been removed, resulting ina material that is virtually exclusively carbon and has a fixed carboncontent in excess of ˜99%. This material is conventionally referred toas a “calcined” or “fully carbonized” char. Secondly, the mass of carbonhas been reduced. The carbon acts as a reductant for the organic orinorganic metallic compound that makes up a part of the precursormixture.

The metallic precursor may be any one of the innumerable organic orinorganic metallic compounds which are possible. The metal component ofthe compound is preferably a transition metal, such as but not limitedto chromium, zirconium, molybdenum, ruthenium, rhodium, palladium,silver, cadmium, zinc, copper, nickel, cobalt, iron, manganese,chromium, vanadium or any combination thereof. However, the metalcomponent may also be comprised of non-transition metals such as:sodium, magnesium, potassium, calcium, tin, lead and others. Upon heattreatment, most organic and some inorganic compounds will undergodecomposition(s) to form a metal oxide. However, this is not arequirement, instead the only critical prerequisite is that the originalcompound or formed intermediate compound(s) can be reduced to itsmetallic state during the heat treatment process. The reduction istypically achieved under an inert atmosphere, in the presence of theaforementioned carbon (char) component. This process results in areduction in solid mass as well as particle size, due to the loss ofnon-metallic elements as gas and an increase in density of the metalrelative to the compound (in most cases).

When an elemental metal is exposed to a carbon source such as char at atemperature of between 400 and 3000 degrees Celsius under inertconditions, the process of catalytic conversion will occur. Hereby the“fully carbonized”, amorphous char will be converted into highlycrystalline graphite over time. In so doing converting one allotrope ofpure carbon into another. The extent and speed of formation of thegraphite is highly dependent on the selected metal but is relativelyinsensitive to the original choice of biomass, mainly because it hasbeen fully carbonized. The exact mechanism of the catalytictransformation is still unknown but two plausible theories have been putforward, namely dissolution-precipitation and carbideformation-decomposition. In the former a carbon source is dissolved inthe metal and graphite is spontaneously precipitated due to differencesin their free energy or level of structural ordering. In the latter anunstable metal carbide is formed, which spontaneously decomposes toyield graphite. The exact formation mechanism is not relevant to thecurrent composition of matter.

Depending on the selected heat treatment temperature and soak time avarying amount of char will be converted into graphite. Overall, thecurrent novel composition of matter can be defined in terms of itselemental composition. Given the fact that the biochar component isfully carbonized to contain in excess of —99% carbon and graphite isalso an allotrope of pure carbon, the composite is a binary mixture withan elemental composition of between 25 to 75 percent carbon and thedifference being made up of a selected pure metal (when an alloy is notused).

In the second instance the carbon may be subdivided into its twoallotropes namely the residual char and formed graphite. The relativeamount of graphite (as a percentage of the carbon present) may bebetween about 55 and about 99.9%wt, with residual char making up theremaining about 45% down to about 0.1%wt. For graphitic materials thispercentage is also known as the “total graphitic carbon” or “TGC”.

While the ideal, model structure of the graphite crystal is well known,real graphitic materials rarely achieve such crystalline perfection. Akey indicator of crystalline imperfection is the so-called “d-spacing”or interlayer distance of the graphene layers comprising the graphitestructure. Rosalind Franklin [3] defined the interlayer spacing ofnon-graphitic (i.e. amorphous) carbons as 0.3440 nm and graphite havingan interlayer spacing of 0.3354 nm. Practical graphitic materials fallsomewhere in between. Depending on the chosen conditions and selectedmetallic precursor the achieved d-spacing will vary. For the novelcomposition of matter under consideration, the required d-spacing may bespecified as 0.3354 nm to 0.3401 nm.

In addition to the elemental composition and form or allotrope of eachcomponent, the novel composition of matter can be further defined interms of the structure of each element. During the heat treatmentprocedure, the metal particles tend to agglomerate and grow in size. Forthe current composition of matter, it is necessary that these remainbelow a certain critical value Smaller particles are better suited to asubsequent purification step due to a higher specific surface area.Thus, in general, the particle sizes of all the components in themixture are required to be less than 1 millimetre.

However, under certain conditions, small amounts of very large metalparticles can sometimes be formed, in some extreme cases up to severalcentimetres. This may be due to factors such as ineffective atmosphericcontrol, choice of heating rate, system geometry, etc. These largeparticles only constitute a very small fraction of the mixture (<10%wtof the metal component). To remove these the entire composite may bescreened or sieved to a particle size of 1 millimetre or smaller afterheat treatment. If a composite includes these abnormal formations, itmay still be considered to fall within the current composition of mattersince they only constitute a minor proportion of the overalldistribution.

The following description of a method to produce the aforementionedmixture is presented for purposes of illustration and description. It isnot exhaustive and does not limit the method to the precise formdisclosed. Modifications and variations are possible in light of thisdisclosure or may be acquired from the practicing of these methods.

The selected biochar and chosen metallic compound may be milled, ifrequired, to ensure an even distribution. The two precursors (biocharand metal component) are then mixed in a ratio of between about 0.1 upto about 10 wt/wt. This can be done under wet or dry conditions. Themixture is heated to a temperature of between 400 and 3000 degreesCelsius in a furnace, oven, kiln, reactor vessel or similar. The heatingmay be achieved by resistively heated electrical elements, microwaves orthe inductive coupling of high frequency electromagnetic fields. Theselected heating method however must ensure homogenous heating of theentire material mass to ensure sufficient conversion and a consistentproduct quality throughout. Thus, surface heating techniques such aslasers or electromagnetic waves with limited sample penetration areexcluded. Such techniques will not achieve the high total graphiticcarbon for the carbon component (TGC >55%wt), stipulated herein as arequirement for this composition of matter. The mixture is soaked forperiods of between 1 minute and 20 hours under inert atmosphere.Following this time, the mixture is cooled, removed from the furnace andsieved to a particle size below 1 millimetre to produce the said mixturewith the desired properties.

The aforementioned properties of the mixture are desirable for achievingthe final set of physical properties and performance characteristics toallow the resulting graphite to be used as a high-performance anode inlithium-ion batteries. The composite can be further processed to enablethe measurement of some of these properties. One such step is theremoval of the metal component. The relative amount and size of themetal allows for its rapid removal using acid leaching. The smallparticles (<1 mm) enable efficient exposure to the acid, while thechosen mass loading of between 25 to 75% wt ensures that leaching timesdo not become excessive. Very high purities exceeding 99.5 wt carbon canbe achieved within hours. If the metal content is reduced, fast leachingis also possible but conversion into graphite will be inadequate,thereby compromising other battery anode properties.

For example, a priority specification for high performance lithium-ionbattery anode material is the achievable electrochemical capacity. Ithas been conclusively demonstrated in academic literature [4,5] that adecrease in d-spacing results in a decrease in electrochemical capacity.Heat treated chars exhibit lower capacities than graphite [6], thus thehigher TGC, the higher the achieved capacity. The high purity, highlycrystalline graphite derived from the mixture (TGC >55%wt) can achievegraphite capacities in excess of 200 mAh/g and as high as 372 mAh/g,thereby satisfying the requirements for lithium-ion batteries.

A second critical specification for high performance lithium-ion batteryanode materials is so-called “first cycle efficiency” or “Coulombicefficiency”. It has been demonstrated that the “Coulombic efficiency” isdirectly correlated to the graphite powder specific surface area [5].The specific surface area depends on a wide range of factors, includingthe choice of biomass source. The structure and intrinsic porositypresent in the biomass structure will, to a large extent, persist allthe way through the process to the graphite present in the mixture. Agraphite surface area range of 0.2 to 50 m²/g or less is desirable forachieving an acceptable “Coulombic efficiency”. The high purity, highdensity graphite derived from this novel mixture composition of mattercomposite has achieved “Coulombic efficiencies” of greater than 60% andas high as 99%, thereby satisfying the requirements for lithium-ionbatteries.

EXAMPLES

The examples described herein are provided for the purpose ofillustrating specific embodiments of the invention and are not intendedto limit the invention in any way. Although the examples describedherein have been used to describe a method, it is understood that suchdetail is solely for this purpose and variations may be made therein bythose skilled in the art without departing from the spirit and scope ofthe overall process.

The microwave laboratory setup which was used to produce these samplesmay be described as follows. A custom designed microwave applicator isused to heat samples to temperatures of up to 2000° C., with a maximumpower input of 3 kW. The applicator arrangement is shown in FIG. 1 . Amicrowave generator delivers power to the applicator via a WR340waveguide auto-tuner, a PTFE window and a passive coupling element. Themicrowave generator is a 2.45 GHz YJ1600-based source (Sairem). A sampleis placed within a crucible and positioned within the applicator,usually on a “pillar” or stand, at a predetermined height to obtain aspecific radiation distributions (see FIG. 2A). The unit is sealed andpurged using nitrogen gas (99.9% pure) at a high flowrate forapproximately 1 hour to establish an inert atmosphere and then a lowerpurge flowrate is used to maintain it. After this the power is graduallyapplied at a rate of 30 W/min to allow the sample to heat up slowly andrapidly achieve steady state at the desired final power. The steadypower setting is chosen to achieve a desired temperature. The finalpower level is then held for a specific time, depending on the desiredoutcome. At this point the sample is glowing red and the cruciblesurface temperature can be measured using a handheld pyrometer throughthe sight glass, as shown in FIG. 2B. Pyrometer readings demonstrated ahigh level of fluctuation and uncertainty, thus a temperature band isreported in the applicable Examples below. Power is then maintainedsteady for a given time frame, after which the generator is turned offand the resulting mixture sample allowed to cool for removal.

Example 1

Sawdust (50 g) from pine trees (pinus radiata) was hydrothermallytreated with deionised water at a temperature of 360 degrees Celsius for20 min in an autoclave. The sample was allowed to cool and then filteredusing a Buchner funnel; the resulting char was dried in a conventionaloven. The dry char (17.5 g) with carbon content around 80%, was combinedwith 9.4 g of Manganese Acetate (tetrahydrate). The resulting mixturewas placed in a crucible and transferred to the microwave applicator.Inert conditions were established using nitrogen gas as described aboveand power was gradually increased at a rate of approximately 30 W/min upto 1.9 kW. Temperature was measured to be between 1700-1900 degreesCelsius. The power was maintained steady for around 5 to 10 minutesafter which the power was cut to the microwave applicator to produce aresulting mixture. Once cooled the sample was sieved to below 1 mm toremove some large metal particles in the mixture, at this point themixture composition can be calculated as shown in Table 1. It was thenleached with 500 ml of concentrated hydrochloric acid overnight,followed by washing with deionised water and filtering with a Buchnerfunnel to produce graphite. The resulting graphite was analysed usingXRD (Bruker D8 Advance diffractometer using a mirror-derived 1mm highparallel beam of cobalt K alpha radiation, weighted mean wavelength1.709026 Angstroms) and SEM (using an ultra-high-resolutionfield-emission microscope: Zeiss Ultra Plus 55 FEGSEM, equipped with anin-lens detection system operating at an acceleration voltage of 1 to 10kV. A working distance of between 1 and 5 mm was used and the powderswere lightly deposited on carbon tape without any additional samplepreparation). The XRD spectra is shown in FIG. 4 and indicates ad-spacing of 0.3355 nm, in addition since no other peaks except thosefor graphite it can be concluded that the sample has a graphite (carbon)purity in excess of 90% wt. Furthermore, since the XRD spectra lacks thebroad, low intensity peak of amorphous carbon at low angles, it can beconcluded that less than 20% of the carbon is not graphitic. A sample ofthe resulting graphite was characterised and found to have a specificsurface area of 26.8 m²/g. The structure of the formed graphite is shownin FIG. 3 , indicating a large, flake-like, anisotropic material withhighly ordered graphite crystals. This experiment produced some largemetal particles in the mixture, examples of which are shown in FIG. 5 .

TABLE 1 Example 1 - Mixture Composition Carbon Yield Metal content Mass(%) (est.) post Carbon of Mn Acetate Metal Carbon Metal Component (g)reduction (g) (%) (g) (%) (%) Dry char 17.5 55% 9.625 82% Mn Acetate 9.422% 2.1 18%

Based on the XRD result it can be assumed that 80% of the carbon isgraphitic, thus the composition of the mixture can be stated as:

-   -   (a) a graphite content of about 66 percent by weight,    -   (b) a metal content of about 18 percent by weight, and    -   (c) a biochar content of about 16 percent by weight.

Example 2

Sawdust (50 g) from pine trees (pinus radiata) was hydrothermallytreated with deionised water at a temperature of 360 degrees Celsius for20 min in an autoclave. The sample was allowed to cool and then filteredusing a Buchner funnel; the resulting char was dried in a conventionaloven. The dry char (10.1 g) with carbon content around 80%, was combinedwith 8.2 g of Manganese Acetate (tetrahydrate). The resulting mixturewas placed in a crucible and transferred to the microwave applicator.Inert conditions were established and power was gradually increased at arate of approximately 30 W/min up to 1.3 kW. Temperature was measured tobe between 1400-1600 degrees Celsius. The power was maintained steadyfor around 5 to 10 minutes after which the power was cut. Once cooledthe sample was sieved to below 1 mm, at this point the mixturecomposition can be calculated as shown in Table 2. It was then leachedwith 500 ml of hydrochloric acid overnight, followed by washing withdeionised water and filtering with a Buchner funnel. The resultinggraphite was analysed using XRD (Bruker D8 Advance diffractometer usinga mirror-derived 1mm high parallel beam of cobalt K alpha radiation,weighted mean wavelength 1.709026 Angstroms) and SEM (using anultra-high-resolution field-emission microscope: Zeiss Ultra Plus 55FEGSEM, equipped with an in-lens detection system operating at anacceleration voltage of 1 to 10 kV. A working distance of between 1 and5 mm was used and the powders were lightly deposited on carbon tapewithout any additional sample preparation). The XRD spectra is shown inFIG. 7 and indicates a d-spacing of 0.3392 nm, in addition since noother peaks except those for graphite it can be concluded that thesample has a graphite (carbon) purity in excess of 90% wt. Furthermore,since the XRD spectra lacks the broad, low intensity peak of amorphouscarbon at low angles, it can be concluded that less than 20% of thecarbon is not graphitic. A sample of the graphite was characterised andfound to have a surface area of 74.0 m²/g. The structure of the formedgraphite is shown in FIG. 6 , indicating a material with smaller, randomcrystallites and a more isotropic structure.

TABLE 2 Example 2 - Mixture Composition Carbon Yield Metal content Mass(%) est. post Carbon of Mn Acetate Metal Carbon Metal Component (g)reduction (g) (%) (g) (%) (%) Dry char 10.1 55% 5.555 75% Mn Acetate 8.222% 1.8 25%

Based on the XRD result it can be assumed that 80% of the carbon isgraphitic, thus the composition of the mixture can be stated as

-   -   (a) a graphite content of about 60 percent by weight,    -   (b) a metal content of about 25 percent by weight and    -   (c) a biochar content of about 15 percent by weight.

Example 3

Sawdust (50 g) from pine trees (pinus radiata) was hydrothermallytreated with pure water at a temperature of 360 degrees Celsius for 20min in an autoclave. The sample was allowed to cool and then filteredusing a Buchner funnel; the resulting char was dried in a conventionaloven. The dry char (26.7 g) with carbon content around 80%, was combinedwith 16.2 g of Manganese Acetate (tetrahydrate). The resulting mixturewas placed in a crucible and transferred to the microwave applicator.Inert conditions were established and power was gradually increased at arate of approximately 30 W/min up to 1.3 kW. Temperature was measured tobe between 1400-1600 degrees Celsius. The power was maintained steadyfor around 30 to 40 minutes after which the power was cut. Once cooledthe sample was sieved to below 1 mm, at this point the mixturecomposition can be calculated as shown in Table 3. It was then leachedwith 500 ml of hydrochloric acid overnight, followed by washing withdeionised water and filtering with a Buchner funnel. The resultinggraphite was analysed using XRD (Bruker D8 Advance diffractometer usinga mirror-derived 1mm high parallel beam of cobalt K alpha radiation,weighted mean wavelength 1.709026 Angstroms) and SEM (using anultra-high-resolution field-emission microscope: Zeiss Ultra Plus 55FEGSEM, equipped with an in-lens detection system operating at anacceleration voltage of 1 to 10 kV. A working distance of between 1 and5 mm was used and the powders were lightly deposited on carbon tapewithout any additional sample preparation). The XRD spectra is shown inFIG. 9 and indicates a d-spacing of 0.3360 nm, in addition since noother peaks except those for graphite it can be concluded that thesample has a graphite (carbon) purity in excess of 90% wt. A sample ofthe graphite was characterised and found to have a surface area of 50.2m²/g. Furthermore, since the XRD spectra lacks the broad, low intensitypeak of amorphous carbon at low angles, it can be concluded that lessthan 20% of the carbon is not graphitic. The structure of the formedgraphite is shown in FIG. 8 , indicating an intermediary betweenflake-like particles and smaller, random crystallites with a moreisotropic structure.

TABLE 3 Example 3 - Mixture Composition Carbon Yield Metal content Mass(%) est. post Carbon of Mn Acetate Metal Carbon Metal Component (g)reduction (g) (%) (g) (%) (%) Dry char 26.7 55% 14.685 80% Mn Acetate16.2 22% 3.6 20%

Based on the XRD result it can be assumed that 80% of the carbon isgraphitic, thus the composition of the mixture can be stated as:

-   -   (a) a graphite content of about 64 percent by weight,    -   (b) a metal content of about 20 percent by weight, and    -   (c) a biochar content of about 16 percent by weight.

Example 4

The graphite from several test runs under similar conditions as thosedescribed in Example 1 to 3, were mixed together to generate a largesample for battery testing. The mixed sample was analysed using XRD andfound to have a d-spacing of around 0.3378 nm as shown in FIG. 10 .Surface area was measured as 52.85 m²/g. The particle size distributionwas verified and the material was found to have an average particle sizeof 29.22 micron as demonstrated in FIG. 11 . The lithium-ion batteryperformance was verified as follows: graphite was coated onto a copperfoil using a suitable binder. After drying circular discs were cut usinga punch and mallet These were combined with lithium metal foil to form acoin cell. The organic electrolyte consisting of LiPF6 and ethylenecarbonate was introduced under inert conditions. The coin cell wassealed and tested using a potentiostat. The electrochemical data wascollected and analysed manually after testing in CR2016 coin cells. FIG.12 shows first charge and discharge cycles at C/20 (C being thetheoretical capacity of graphite which is 372 mAh/g) at constant currentrate. The specific capacity obtained from the first discharge cycle forthe CarbonScape graphite in the half cell is 410.87 mAh/g while thecharge capacity is 275 mAh/g. This gives a first cycle or “Coloumbic”efficiency of 66.46%, thus the graphite exhibits properties which aresuitable for use in lithium-ion batteries.

Example 5

Sawdust (˜10 g) from pine trees (pinus radiata) was combined with around17.6 g of Manganese Acetate (tetrahydrate). The resulting mixture wasplaced in a crucible and heated in a conventional, electrically heatedfurnace (RD WEBB Aircooled Vacuum Furnace model RD-G). Inert conditionswere established by purging with Argon gas (>99.9%) and the temperaturewas increased at a ramp rate of 10 degrees per minute. Final temperaturewas set at 1750 degrees Celsius. The temperature was maintained steadyfor 180 minutes after which the furnace was switched off. Once cooledthe sample was sieved to below 1 mm, at this point the mixturecomposition can be calculated as shown in Table 4. It was then leachedwith 500 ml of hydrochloric acid overnight, followed by washing withdeionised water and filtering with a Buchner funnel. The resultinggraphite was analysed using XRD (Bruker D8 Advance diffractometer usinga mirror-derived 1mm high parallel beam of cobalt K alpha radiation,weighted mean wavelength 1.709026 Angstroms). The XRD spectra is shownin FIG. 13 and indicates a d-spacing of 0.3358 nm, in addition since noother peaks except those for graphite it can be concluded that thesample has a graphite (carbon) purity in excess of 90% wt. Using theestablished correlation between d-spacing and discharge capacity [5],this material may be estimated to have an electrochemical capacity ofaround 351 mAh/g. Furthermore, since the XRD spectra lacks the broad,low intensity peak of amorphous carbon at low angles, it can beconcluded that less than 20% of the carbon is not graphitic. A sample ofthe graphite was characterised and found to have an unexpectedly lowsurface area of 5.439 m²/g. Using the established correlation between“Coulombic efficiency” and specific surface area [5], this material maybe estimated to have a “Coulombic efficiency” of around 85%.

TABLE 4 Example 5 - Mixture Composition Carbon Yield Metal content Mass(%) est. post Carbon of Mn Acetate Metal Carbon Metal Component (g)reduction (g) (%) (g) (%) (%) Sawdust 10 20% 2 34% Mn Acetate 17.6 22%3.9 66%

Based on the XRD result it can be assumed that 80% of the carbon isgraphitic, thus the composition of the mixture can be stated as:

-   -   (a) a graphite content of about 27 percent by weight,    -   (b) a metal content of about 66 percent by weight, and    -   (c) a biochar content of about 7 percent by weight.

Example 6

Pyrolyzed hard wood charcoal (˜10 g) obtained from “Solid Energy” in NewZealand was milled and sieved to below 200 microns. The char, with acarbon content of around 70%, was combined with around 6.6 g ofManganese Oxide. The resulting mixture was placed in a crucible andheated in a conventional, electrically heated furnace (RD WEBB AircooledVacuum Furnace model RD-G). Inert conditions were established by purgingwith Argon gas (>99.9%) and the temperature was increased at a ramp rateof 10 degrees per minute. Final temperature was set at 1750 degreesCelsius. The temperature was maintained steady for 180 minutes afterwhich the furnace was switched off. Once cooled the sample was sieved tobelow 1 mm, at this point the mixture composition can be calculated asshown in Table 5. It was then leached with 500 ml of hydrochloric acidovernight, followed by washing with deionised water and filtering with aBuchner funnel. The resulting graphite was analysed using XRD (Bruker D8Advance diffractometer using a mirror-derived 1mm high parallel beam ofcobalt K alpha radiation, weighted mean wavelength 1.709026 Angstroms).The XRD spectra is for this sample is also shown in FIG. 13 andindicates a d-spacing of 0.3362 nm, in addition since no other peaksexcept those for graphite it can be concluded that the sample has agraphite (carbon) purity in excess of 90% wt. Using the establishedcorrelation between d-spacing and discharge capacity [5], this materialmay be estimated to have an electrochemical capacity of around 346mAh/g. Furthermore, since the XRD spectra lacks the broad, low intensitypeak of amorphous carbon at low angles, it can be concluded that lessthan 20% of the carbon is not graphitic. A sample of the graphite wascharacterised and found to have an exceptionally low surface area ofjust 0.204 m²/g. Using the established correlation between “Coulombicefficiency” and specific surface area [5], this material may beestimated to have a “Coulombic efficiency” of around 96%.

TABLE 5 Example 6 - Mixture Composition Carbon Yield Metal content Mass(%) est. post Carbon of Mn Oxide Metal Carbon Metal Component (g)reduction (g) (%) (g) (%) (%) Dry Char 10 80% 8 66% Mn Oxide 6.6 63% 4.234%

Based on the XRD result it can be assumed that 80% of the carbon isgraphitic, thus the composition of the mixture can be stated as:

-   -   (a) a graphite content of about 53 percent by weight,    -   (b) a metal content of about 34 percent by weight, and    -   (c) a biochar content of about 13 percent by weight.

The schematic outline of the overall process is shown in FIG. 14 , wherebiomass in particulate form (1) is processed to graphite powder (4),suitable for use in battery anodes. The biomass (1) is converted tobiochar (2) in particulate form. The biochar (2) is then combined with ametal in particulate form and heat treated to form the composition ofmatter (3). The composition of the mixture (3) of biochar, graphite andmetal is then used to form the graphite powder (4). The graphite powder(4) is created by processing the mixture (3) as described above in theExamples.

As can be seen from the examples and FIG. 14 , it is possible to achievea graphite powder having properties suitable for use as a highperformance lithium-ion battery anode powder. Due to the unique startingpoint of the process, compared to conventional natural and syntheticgraphite, the resulting anode powder has been found to be unique interms of its structure and performance. Because of this, the graphitepowder achieved exhibits a distinctive set of performancecharacteristics and is capable of outperforming both natural andsynthetic graphite in specific lithium-ion battery applications. Inaddition, the current graphite is the only material with a negative CO₂emissions footprint. This makes it an environmentally friendly option.

What is claimed is:
 1. A method of producing a mixture a mixture ofbiochar, a metal, and graphite, comprising: i) thermally treatingbiomass in particulate form at a temperature of between 200 and 1000degrees Celsius to form a particulate biochar; ii) combining theresulting biochar with a particulate metal compound combining theresulting biochar with a particulate metal compound in a wet or a dryform to create a precursor mixture; iii) heating the precursor mixtureto between about 400 to about 3000 degrees Celsius under inertconditions to form a graphite containing mixture; iv) sieving the finalmixture to below about 1 mm particulate size to produce a mixture having(a) a graphite content of between about 25 to 65 percent by weight, (b)a metal content of between about 15 to 75 percent by weight and (c) abiochar content of between 1 and 35 percent by weight.
 2. The method asclaimed in claim 1, wherein the biomass is thermally treated in water ina hydrothermal step.
 3. The method as claimed in claim 1, wherein thebiomass is thermally treated under inert conditions in a dry pyrolysisstep.
 4. The method as claimed in claim 1, wherein the biomass isselected from forestry residue, sawdust, wood chip or other wood-basedmaterial.
 5. The method as claimed in claim 1, wherein the biomassparticles are less than about 10 mm
 6. The method as claimed in claim 1,wherein the mixture has a total graphitic carbon content of great thanabout 55% by weight.
 7. The method as claimed in claim 1, wherein themethod includes one or more of the following steps, selected from: (a)purification; (b) washing and filtering the resulting graphite; (c)densification; and (d) carbon coating.
 8. A graphite powder producedfrom a method as claimed in claim
 1. 9. A high performance lithium ionbattery anode powder produced from a method as claimed in claim 1.